<h2>DESCRIPTION</h2>

<em>i.eb.soilheatflux</em> calculates the soil heat flux approximation (g0)
after Bastiaanssen (1995). The main reference for implementation is Alexandridis, 2009.

It takes input of Albedo, NDVI, Surface Skin temperature, Net Radiation (see 
<em>r.sun</em>), time of satellite overpass, and a flag for the Roerink empirical modification from the HAPEX-Sahel experiment.

The "time of satellite overpass" map can be obtained as follows:
<ul>
<li>MODIS: a related sub dataset is included in each HDF file, and simply 
    to be imported as a raster map;</li>
<li>Landsat: to be generated as map from the overpass time stored in
    the metadata file (given in Greenwich Mean Time - GMT), see below.</li>
</ul> 

For Landsat, the overpass map can be computed by using a two-step method:

<div class="code"><pre>
# 1) extract the overpass time in GMT from metadata file

i.landsat.toar -p input=dummy output=dummy2 \
   metfile=LC81250452013338LGN00_MTL.txt lsatmet=time
# ... in this example approx. 03:12am GMT

# 2) create map for computational region of Landsat scene
g.region rast=LC81250452013338LGN00_B4 -p
r.mapcalc "overpasstime = 3.211328"
</pre></div>

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<h2>EXAMPLE</h2>

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i.eb.soilheatflux ...
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<h2>SEE ALSO</h2>

<em>
<a href="r.sun.html">r.sun</a>,
<a href="i.albedo.html">i.albedo</a>,
<a href="i.emissivity.html">i.emissivity</a>,
<a href="i.eb.hsebal01.html">i.eb.hsebal01</a>,
<a href="i.eb.evapfr.html">i.eb.evapfr</a>
<a href="i.landsat.toar.html">i.landsat.toar</a>
</em>

<h2>REFERENCES</h2>

<p>Bastiaanssen, W.G.M., 1995.
  Estimation of Land surface parameters by remote sensing under clear-sky 
  conditions. PhD thesis, Wageningen University, Wageningen, The Netherlands.
 (<a href="http://edepot.wur.nl/206553">PDF</a>)
 
<p>Chemin Y., Alexandridis T.A., 2001. Improving spatial resolution of ET seasonal
  for irrigated rice in Zhanghe, China. Asian Journal of Geoinformatics. 5(1):3-11,2004. 

<p>Alexandridis T.K., Cherif I., Chemin Y., Silleos N.G., Stavrinos E.,
Zalidis G.C. Integrated methodology for estimating water use in Mediterranean
agricultural areas. Remote Sensing. 2009, 1, 445-465. 
(<a href="http://www.mdpi.com/2072-4292/1/3/445">PDF</a>)

<p>Chemin, Y., 2012. 
A Distributed Benchmarking Framework for Actual ET Models, 
in: Irmak, A. (Ed.), Evapotranspiration - Remote Sensing and Modeling. InTech.
(<a href="http://www.intechopen.com/books/evapotranspiration-remote-sensing-and-modeling/a-distributed-benchmarking-framework-for-actual-et-models">PDF</a>)

<h2>AUTHOR</h2>

Yann Chemin, Asian Institute of Technology, Thailand<br>

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